DNA repair and recovery of RNA synthesis following exposure to ultraviolet light are delayed in long genes

The kinetics of DNA repair and RNA synthesis recovery in human cells following UV-irradiation were assessed using nascent RNA Bru-seq and quantitative long PCR. It was found that UV light inhibited transcription elongation and that recovery of RNA synthesis occurred as a wave in the 5’-3’ direction with slow recovery and TC-NER at the 3’ end of long genes. RNA synthesis resumed fully at the 3’-end of genes after a 24-hour recovery in wild-type fibroblasts, but not in cells deficient in transcription-coupled nucleotide excision repair (TC-NER) or global genomic NER (GG-NER). Different transcription recovery profiles were found for individual genes but these differences did not fully correlate to differences in DNA repair of these genes. Our study gives the first genome-wide view of how UV-induced lesions affect transcription and how the recovery of RNA synthesis of large genes are particularly delayed by the apparent lack of resumption of transcription by arrested polymerases. Overall design: This study is composed of three identical experiments run in three different cell lines. For each experiment, there is one control (mock irradiated cells) and four test samples (0h, 2h, 6h and 24h after UV 10J irradiation).